Power press with overload protection

ABSTRACT

A power press with an eccentric for the vertical reciprocation of a hammer has its drive shaft eccentrically journaled in bearing sleeves whose common axis is horizontally offset from the shaft axis whereby a torque is exerted upon the sleeves by the reaction force of a workpiece struck by the hammer. The sleeves, which are themselves rotatably mounted in the press frame, are integral with horizontally extending arms which tend to swing about the sleeve axis in response to the exerted torque, such swinging being normally prevented by a frictional, fluidic or elastic counterforce acting upon the free ends of the arms.

United States Patent [111 3,908,436

Bothe Sept. 30, 1975 [5 4] POWER PRESS WITH ()VERLOAD 1,020,693 2/1966 United Kingdom 72/432 PROTECTION 590,785 4/1959 Italy 100/257 [75] inventor: Werner Bothe, Dusseldorf, Germany g [73] Assignee: Maschinenfabrik Hasenclever 'fi f f f g L Gmb Dusseldorf Germany ASbIS/(Ull .\(II71III) ene ros y Attorney, Agent, or FirmKarl F. Ross; Herbert [22] Filed: May 1, 1974 Dubno 211 Appl. No.: 466,001

[57] ABSTRACT A power press with an eccentric for the vertical reciprocation of a hammer has its drive shaft eccentrically journaled in bearing sleeves whose common axis is horizontally offset from the shaft axis whereby a torque is exerted upon the sleeves by the reaction force of a workpiece struck by the hammer. The sleeves, which are themselves rotatably mounted in the press frame, are integral with horizontally extending arms which tend to swing about the sleeve axis in response to the exerted torque, such swinging being normally prevented by a frictional, fluidic or elastic counterforce acting upon the free ends of the arms,

10 Claims, 6 Drawing Figures US. Patent Sept. 30,1975 Sheet 2 of5 3,908,436

FIG. 2

(1 li M 1 h) FIG. 3

Sheet 4 of 5 3,908,436

: FIG. 4

U.S. Patent Sept. 30,1975

U.S. Patent Sept. 30,1975 Sheet50f5 3,90,436

FIG. IA

FIG. 5

1 POWER PRESS WITH OVERLOAD PROTECTION FIELD OF THE INVENTION My present invention relates to a power press of the type wherein a hammer or ram is reciprocated (usually vertically) toward and away from an anvil, fastened to the press frame, for the purpose of deforming an interposed workpiece.

BACKGROUND OF THE INVENTION In commonly assigned U.S. Pat. No. 3,726,l23 I have disclosed and claimed a press of this general type wherein a horizontal shaft, journaled in the press frame, carries an eccentric disk which is linked with the reciprocable forging hammer through the intermediary of a yoke-shaped pressure block. The coupling includes an eccentric sleeve whose angular position can be adjusted with the aid of a servomotor to vary the width of the working gap formed between anvil and hammer in the bottom position of the latter. The shaft carrying a flywheel is driven by a motor through a clutch which, as is generally the case in machinery of this type, can slip in the presence of overload to prevent damage to the equipment.

In another commonly assigned U.S. Pat. No. 3,521,475, I have shown a forging press in which the eccentric disk on the drive shaft bears upon the hammer through the intermediary of a generally crescentshaped force-transmitting member received in a complementary socked of a forging head or hammer with freedom of limited angular displacement. In such a press a maximum amount of energy can be transmitted to the workpiece with a relatively short hammer stroke so that the construction is very compact. The reduction in stroke length requires, in turn, a higher degree of stiffness of the structure, i.e. a reduction in its elasticity, in order that the workpiece may be deformed within established tolerance limits. In such a system the overload protective clutch must therefore be more accurately calibrated.

Thus, it has been found in practice that the actual deformation phase, i.e. the terminal part of the working stroke of the hammer, should be limited to not more than about l to of shaft rotation if objectionable stresses are to be avoided. With such a delayed buildup of the working pressure, only relatively shallow deformations of a workpiece can be carried out. Operations requiring larger displacements of the hammer under load, e.g. for deep-drawing or for punching or deburring heavy sheets, are excluded.

Moreover, the usual friction clutches used in such presses are not reliable safety devices since the maximum torque to be transmitted, beyond which the clutch is supposed to slip, may vary considerably on account of wear or changes in fluid pressure.

OBJECTS OF THE INVENTION The general object of my invention is to provide a power press of this character which avoids the afore stated drawbacks.

A more particular object is to provide such a press with effective overload-protection means of simple construction which can also be used to adjust the width of the working gap.

SUMMARY OF THE INVENTION In accordance with my present invention, the drive shaft eccent'rically coupled with the reciprocating hammer is eccentrically journaled in a bearing sleeve (or,

in most instances, in a pair of such sleeves) which is rotatably journaled in the press frame and is centered on 5 a swing axis offset from the shaft axis in a direction generally transverse to the path of hammer reciprocation, i.e. substantially horizontally if the hammer reciprocates vertically as is usually the case. Owing to this relative offsetting of the two axes, the reaction force of a workpiece struck by the hammer exerts a torque upon the sleeve or sleeves tending to rotate same about the aforementioned swing axis; such rotation is normally prevented by yieldable restraining means engaging a member integral with the sleeve at a location remote from that swing axis.

According to a more particular feature of my invention, the member integral with the sleeve is a lever arm extending therefrom in the aforementioned generally transverse (usually horizontal) direction, preferably on the side opposite the shaft axis. With the moment arm of the reaction force substantially shorter than that of the restraining force, the latter force may be relatively weak. Also, this force does not intervene in the power train between the shaft drive and the hammer so that the restraining elements are not subject to undue wear. The power train may include a flywheel adapted to be coupled to the shaft through a clutch having no overload-protection function.

The restraining force can be exerted in various ways, e.g. frictionally, fluidically or elastically. In the lastmentioned instance an automatic restoration to normal operating position occurs after the overload condition has ended. In any case, pursuant to a further feature of my invention, the engagement between the lever arm able to alter the normal distance of the shaft axis from the anvil and, thereby, the width of the working gap.

BRIEF DESCRIPTION OF THE DRAWING The above and other features of my invention will now be described in detail with reference to the accompanying drawing in which:

FIG. 1 is a side-elevational view of a power press embodying my invention;

FIG. 1A is a cross-sectional detail view taken on the line IA Ia of FIG. 1;

FIG. 2 is a sectional elevation taken on the line II II of FIG. 1;

FIG. 3 is an elevational view similar to FIG. 1, partly in section on the line III III of FIG. 2;

FIG. 4 is an elevational view similar to FIG. 1, showing a modified press; and

FIG. 5 is a fragmentary elevational view illustrating another modification.

SPECIFIC DESCRIPTION In FIGS. 1 3 I have shown a press combining features of my two above-identified prior US. patents. A press frame 1 is rigid with a bed or anvil 2 confronting a ram or hammer 3 which is vertically reciprocable thereabove, the frame having a pair of lateral openings 22 for the introduction and withdrawal of workpieces just above the anvil 2. A horizontal shaft 4, carrying a flywheel 6, is coupled with that flywheel through the intermediary of a friction clutch 5; the shaft is driven by a motor 23, FIG. 3, through a belt 24 passing around the flywheel 6. Motor 23 is carried on a bracket 25 or arms and the restraining means can be made adjustwhose attitude relative to frame 1 is adjustable by a linkage including a turnbuckle 26 to enable proper tensioning of the belt. With flywheel 6 rotating at constant speed, clutch is normally released and is actuated (e.g. hydraulically) whenever the hammer 3 is to be reciprocated.

An eccentric disk 7 rigid with shaft 4 is coupled with the hammer 2 in the general manner taught in my prior US. Pat. No. 3,521,475 referred to above, i.e. through a ring 8 which embraces the disk 7 and has a crescentshaped downward extension 9 swivelably received in a recess 10 of hammer 3. Antifriction layers 27 and 28 separate the ring 8 and its force-transmitting extension 9 from the disk 7 and the hammer 3, respectively.

Disk 7 is flanked by a pair of sleeves 11 forming eccentric bearings for the shaft 4, these sleeves being in turn rotatably lodged in journals 12 formed by press frame 1. As best seen in FIG. 1, the sleeves 11 are centered on a swing axis A which is horizontally spaced from the axis B of shaft 4. Furthermore, each sleeve is integral with a lateral lever arm 13 extending generally horizontally along the outer frame wall in the direction away from shaft axis B. Thus, the reaction force of a workpiece engaged by hammer 3 is in line with shaft axis B anf therefore exerts a moment upon the sleeve 11 tending to swing the arm 13 counterclockwise as viewed in FIG. 1. Such swinging is resisted by a protective restraining device, generally designated 14, which comprises a bolt 18 passing through an extension 1a of frame 1 and through an arcuate slot of arm 13, this slot being centered on axis A. Device 14 is, of course, duplicated on opposite sides of the press frame. Bolt 18, threaded into frame extension 1a and secured by a counternut 18a, has a head 18b (see FIG. 1A) bearing upon a coil spring 19 which in turn exerts pressure on a friction disk 17 whose diameter substantially exceeds the width of slot 15 whereby parts of that friction disk rest on roughened surfaces 17 along the edges of the slot.

The friction exerted by disk 17 upon arm 13 normally prevents that arm from yielding to the reaction force of a workpiece deformed between anvil 2 and hammer 3. In the event of overload, however, this force will give way and protect the system against objectionable stresses.

7 It will be apparent that a loosening of counternut 18a enables the pressure of spring 19 to be adjusted between wide limits. Furthermore, upon a slackening of the spring pressure, arm 13 may be rotated about its swing axis A to vary the minimum spacing of the hammer 3 from the anvil 2. For this purpose, the free end 13a is provided with rack teeth and engaged by a pinion 29 which can be manually rotated with the aid of a key or a wrench.

A crest 8a of ring 8 bears, through the intermediary of another antifriction layer 30, upon a concave guide rib 31 depending from a yoke 32 integral with hammer 3, substantially as disclosed in my prior US. Pat. No. 3,521,475. Yoke 32 serves to entrain the hammer during the upstroke.

In FIG. 4 I have shown aa generally similar press whose bearing sleeves 11 are provided with modified arms 13' projecting by their free ends beyond the frame 1. A protective restraining device 14' comprises a hydraulicjack whose double-acting piston 33 is articulated to the two arms 13' (only one shown) via a rod 34 interconnecting these arms. Cylinder or jack 20 is filled with hydraulic fluid on both sides of its piston head, this fluid having been introduced by a nonillustrated pump via a line 35 with branches 35a and 35b. A valve disconnects, in its illustrated position, the branches 35a and 35b from supply conduit 35 and interconnects them in a closed circuit including a pressure-relief valve 22 suitable calibrated by a loading spring 21a. When the press is overloaded, valve 21 yields and allows the hydraulic fluid to circulate so that piston 33 can slide and arm 13' can swing about axis A to relieve the reaction force. It will be evident that, upon a manual unblocking of relief valve 21, the arms 13' can be moved into a position other than the one illustrated in order to change the width of the working gap.

In FIG. 5 I have shown part of a press, otherwise similar to that of FIGS. 1 4, whose frame 1 carries a pair of brackets 37 (only one shown) which are adjustably mounted thereon with the aid of screws 38 transversing vertical slots 39. Lugs 40 on bracket 37 support a vertical bolt 41 which passes with clearance through an opening in the free end of an arm 13", this arm being held in its illustrated position by the countervailing pressures of two opposing prestressed coil springs 42a and 42b on bolt 41. Vertical adjustment of bracket 37, upon a loosening of screws 38, again enables the selection of an operating position in which the hammer has a predetermined minimum spacing from the anvil.

In all the described embodiments it is thus possible to select a restraining force effectively resisting, within a predetermined load range, the tendency of arms 13, 13' or 13" to swing out of their normal, generally horizontal position in response to the reaction force of a workpiece deformed between anvil and hammer.

I claim: 1. A power press comprising: a stationary frame forming a fixed anvil; a hammer co-operating with said anvil for deforming a workpiece interposed therebetween;

drive means for reciprocating said hammer on said frame, said drive means including a shaft, an eccentric coupling between said shaft and said hammer, and sleeve means forming an eccentric bearing for said shaft, said sleeve means being rotatably journaled in said frame and being centered on a swing axis offset from the shaft axis in a direction generally transverse to the path of hammer reciprocation whereby the reaction force of a workpiece struck by said hammer exerts a torque upon said sleeve means tending to rotate same about said swing axis;

a member integral with said sleeve means rotatable therewith about said swing axis; and

yieldable restraining means engaging said member at a location remote from said swing axis for normally preventing any rotation thereof.

2. A press as defined in claim 1 wherein said restraining means is adjustable for varying the normal distance between said shaft axis and said anvil.

3. A press as defined in claim 1 wherein said member comprises an arm extending from said sleeve in said generally transverse direction, said arm having a free end engaged by said restraining means.

4. A press as defined in claim 3 wherein said sleeve and said arm are duplicated on opposite sides of said hammer.

5. A press as defined in claim 3 wherein said restraining means comprises a friction coupling between said arm and said frame.

6. A press as defined in claim 5 wherein said arm is provided with an arcuate slot centered on said swing axis, said friction coupling including a bolt on said frame traversing said slot and a spring-loaded washer on said bolt bearing upon said arm along the edges of said slot.

7. A press as defined in claim 3 wherein said restraining means comprises a fluid cylinder anchored to said frame, a double-acting piston in said cylinder linked with said arm, and a fluid circuit connected to said cylinder, said circuit including a pressure-relief valve normally blocking fluid circulation from one side of said piston to the other.

8. A press as defined in claim 3 wherein said restraining means comprises a pair of counteracting pre-- a clutch on said shaft for rotary entrainment of same. 

1. A power press comprising: a stationary frame forming a fixed anvil; a hammer co-operating with said anvil for deforming a workpiece interposed therebetween; drive means for reciprocating said hammer on said frame, said drive means including a shaft, an eccentric coupling between said shaft and said hammer, and sleeve means forming an eccentric bearing for said shaft, said sleeve means being rotatably journaled in said frame and being centered on a swing axis offset from the shaft axis in a direction generally transverse to the path of hammer reciprocation whereby the reaction force of a workpiece struck by said hammer exerts a torque upon said sleeve means tending to rotate same about said swing axis; a member integral with said sleeve means rotatable therewith about said swing axis; and yieldable restraining means engaging said member at a location remote from said swing axis for normally preventing any rotation thereof.
 2. A press as defined in claim 1 wherein said restraining means is adjustable for varying the normal distance between said shaft axis and said anvil.
 3. A press as defined in claim 1 wherein said member comprises an arm extending from said sleeve in said generally transverse direction, said arm having a free end engaged by said restraining means.
 4. A press as defined in claim 3 wherein said sleeve and said arm are duplicated on opposite sides of said hammer.
 5. A press as defined in claim 3 wherein said restraining means comprises a friction coupling between said arm and said frame.
 6. A press as defined in claim 5 wherein said arm is provided with an arcuate slot centered on said swing axis, said friction coupling including a bolt on said frame traversing said slot and a spring-loaded washer on said bolt bearing upon said arm along the edges of said slot.
 7. A press as defined in claim 3 wherein said restraining means comprises a fluid cylinder anchored to said frame, a double-acting piston in said cylinder linked with said arm, and a fluid circuit connected to said cylinder, said circuit including a pressure-relief valve normally blocking fluid circulation from one side of said piston to the other.
 8. A press as defined in claim 3 wherein said restraining means comprises a pair of counteracting prestressed springs bearing upon said arm and said frame.
 9. A press as defined in claim 3 wherein said swing axis lies between said free end and said shaft axis.
 10. A press as defined in claim 1, further comprising a flywheel loosely carried on said shaft, transmission means linking said flywheel with said drive means, and a clutch on said shaft for rotary entrainment of same. 